Hydraulic metering fuse



April 8, 1952 D. A. STARK HYDRAULIC METERING FUSE 2 SHEETSSHEET 1 Filed July 10, 1945 I In; verb-5 07"" fiaajfd a. Ji czrv April 8, 1952 D. A. STARK HYDRAULIC METERING FUSE 2 SHEETSSHEET 2 Filed July 10, 1945 Patented Apr. 8, 1952 HYDRAULIG METERING FUSE Donald A. Stark, Chicago; Ill., a'ssign'orto William Waterman," Chicago, Ill.

Application July 10, 1945, Serial No. 604,215

13 Claims.

This invention relates to so-called fuses for altering or interrupting fluid flow, and particularly to metering fuses designed to operate after a predetermined volume of flow. Among other objects, the invention aims to provide means for increasing the metering range of the fuse and particularly for adapting fuses to meter low rates of flow.

The nature of the invention and other objects and advantages thereof may be readily understood by reference to illustrative fuses adapted for metering low rates of flow and shown in the accompanying drawings.

In said drawings:

- Fig. 1 is a longitudinal section of a fuse;

Fig. 2 is a cross section taken onthe plane 2-2 of Fig. 1;

Fig. 3 is a cross section taken on the plane 3-3 of Fig. 1 and showing the broken plane l-l on which Fig. 1 was taken; and

Fig. 4 is a longitudinal section of a different form of fuse embodying the present invention.

For purposes of illustration the invention is here shown applied to two different types of metering fuses disclosed respectively in Waterman application Serial 525,275, now Patent 2,512,190, and Waterman Patent 2,354,161. But it will be apparent that the principle of the invention is not limited to these types of fuses.

In fuses-of the type to which the invention is shown applied, the fuse valve operates to alter the fluid flow (in this case out off the flow) after predetermined volume of flow has passed through the line regardless of the pressures involved, and in this instance also regardless of the variation in viscosity of the fluid. As soon as flow starts a valve element starts to move toward its seat which it reaches after a predetermined volume offlow. Fuses of this type protect against excessive loss of fluid in the event of line breakage; they permit such volume of fluid to flow; (preferably a slight additional amount as a safety factor) as is required to operate a particular instrumentality, such as a piston, and close the line (to prevent further loss) if the flow exceeds thisamountas would be the case under abnormal situations, such as fracture of the line or excessive leakage from whatever cause.

vIt has heretofore been necessary to render the fuse. insensitive to all closing forces-except only theforce of fluid flow. Otherwise extraneous forces such as vibration, inertia, and gravity might cause closing of the line. Inertia forces are particularly severe in aircraft; sudden changes in direction, such as pulling out of a dive, can easily increase gravity and inertia forces to many times gravity. Restraining means such as friction or a spring (e. g. spring 38 in Waterman Patent 2,354,161) have been employed to resist closing of the fuse valve by such extraneous forces, but obviously such restraining means render the fuse insensitive to low flow (such as might be caused by a small fracture or leak in the line) which exerts a force insuflicient to overcome the restraining means. The fuse therefore is insensitive to low flow whether it results from leakage or is an incident to normal operation.

While it is possible for a given rate of flow (even though it be small) to design a fuse so that the force of flow will be sufficient to operate the fuse against a spring or other restraint, such design could not be employed for other rates of flow, and it is of the utmost practical importance that a single design be applicable to a wide range of flow rates.

According to the present invention a fuse valve is unbiased and free to respond to flow however small, yet it is held against a closing movement by other forces such as inertia, gravity, vibration, etc. This result is obtained as presently explained'in detail by holding the fuse valve against movement toward its seat by a device itself releasable only by flow and insensitive to other forces.

In the fuse illustrated in Fig. 1, being the type shown in said Waterman application, the fuse valve H1 is moved toward its seat I I by small pressure drop in the fuse caused by the major flow which passes around the valve and which induces a relatively small auxiliary or divided flow to move the valve. The rate of such auxiliary flow determines the closing or metering of the fuse thereby imposing substantially no restriction on the main flow. As more fully described in said Waterman-application, the valve 10 in the form of a piston operates in a'sleeve or cylinder 12 mounted inside the larger fuse housing I3 leaving asubstantial space I M around the cylinder 12 through which the main flow passes.

Flow enters the fuse housing l3 through a standard threaded coupling element l5 which itself is threaded into the housing and sealed thereto by a sealing ring [6. The opposite end of the housing is provided with a similar stand ard coupling element 11, in this case integral with the housing. Flow entering passage I8 is deiiected laterally through passages iii in the head as to the main passage l4 around the valve and re-enters the central space H of the fuse through control holes 22 in advance of the valve seat ll, so that seating of valve l0 would cut oil flow. A minor portion of the flow, 1. e. the so-called auxiliary stream, passes through control orifice 23 (which it reaches through passages 24 in head 20) and acts on piston 25 with which the valve I is incorporated. Control holes 22 and the passage I 4 are designed, as explained more fully in said Waterman application, to provide a slight pressure drop in reaching the passage 2|, which pressure drop induces the flow through control orifice 23. The latter is adjustable, as presently explained, and its size determines the speed of advance of piston 25 and valve ID towards its seat and therefore the volume of flow passing through the fuse before the valve seats and interrupts further flow. As further explained in said Waterman application, it is possible by proper design of such control holes 22, passage l4, and control orifice 23, to obtain a substantially constant ratio of flow between the main and auxiliary streams regardless of variation of viscosity, so that the metering action of the fuse is not affected by such variation in viscosity. This is particularly important for oils, but relatively less important where the temperature is reasonably constant or the fluid is a light liquid or gas where the change in viscosity can be ignored.

In the present fuse the spring which operated to prevent advance of valve Hi by extraneous forces other than flow, has been replaced by a device which in this case is flow responsive and which prevents advance of piston 25 and valve 1 ll. Such device is here shown in the form of a piston 26 which blocks passage 2| to free escape of the fluid from the fuse. An extension 21 on piston 26 bears against the end of valve l0 and holds it against movement toward its seat unless and until piston 26 is moved. The latter is held against piston 25 by a spring 28 which is strong enough to prevent movement of valve against extraneous forces but which nevertheless because of the substantial area of piston 26 readily yields under a very low pressure drop created when fluid starts to flow through the housing. For convenience, this pressure drop is referred in the claims as fluid pressure. In practice valve l0 and its piston 25 are very light in weight and spring 28 need be precompressed to exert a force only about four or five times the weight of the valve and its piston.

Except where rendered insensitive to predetermined minimum flow as later explained, any flow however light is therefore sufiicient to move piston 26 against compression of its spring and thereby release valve l0 so that it responds at once to flow. When piston 26 and its extension 21 have been moved sufliciently to clear cylinder 12, it uncovers ports 29 in cylinder 38. Thus flow may pass out of the fuse through ports 29 and the passage 3! surrounding cylinder 30 from which passage fluid reaches the exit passage 32 through radial passages 33 in the head 34. Cylinder 30 is sealed inside housing [3 by the sealing ring !3' which prevents short circuiting of the fluid.

Upon interruption of flow, spring 28 returns piston 26 and valve It! to initial position, but return flow may nevertheless freely traverse the fuse through the check valve 35 which in this instance is carried in the head of piston 26 and inside the projection 21. A spring 36 seats the valve 35 on its seat 31 but readily yields on return flow to permit fluid to reach control holes 22 through ports 38.

Control orifice 23 is advantageously designed to embody a check valve which permits free escape of fluids inside piston 25 (when the latter returns) so as not to restrict return of the latter as would be the case if return flow were obliged to pass through orifice 23. As shown particularly in Figs. 1 and 2 the orifice 23 is in the form of a movable disc which on forward flow rests on the edge 40 of the central passage 4|" in the orifice fitting 42. Return flow through passage 4| raises orifice 23 from its seat and escapes through the space 4 3 underneath the orifice. The latter is limited in its movement by a surrounding cylinder 44 having a central bore 45 extending only partly through the cylinder and providing a space for the orifice disc 23 and the projecting tip 46 of the orifice fitting 42. Auxiliary bores 41 passing through the cylinder 44 communicating with the space 43 permit escape of the fluid to the central space 48 with which the radial passages 24 connect. The central bore 45 is counterbored at 49 to provide a space above the orifice through which return fluid passing through the orifice may escape into the auxiliary bores 41. The orifice fitting and cylinder 44 are enclosed by housing 50 having a shoulder 55 against which cylinder 44 seats. A spring ring 52 holds the fitting in place and a sealing ring 53 prevents leakage around the orifice and its fitting.

The orifice housing 50 is advantageously made longitudinally adjustable relative to the head 20 for which purpose it is provided with a screw threaded tip 54 screwed into head 20. It is also provided with an extension 55 adapted to engage the inner face of valve piston 25 and limit its return movement. By this means relatively fine metering adjustments may be made. Obviously the return position of valve Ill determines the volume metered by the fuse. The threaded tip 54 is advantageously provided with a tool receiving recess in the form of a screwdriver slot 56 by means of which such adjustments may be made while the fuse is completely assembled.

Major changes in the metering capacity of the fuse are advantageously made by varying the size of the orifice 23. This is effectively accomplished by employing orifice plates with orifices 23 of varying sizes which may be substituted one for the other. The fine adjustments are made by means of the threaded tip 54 as explained above. The friction and sealing ring 51 of synthetic rubber or the like is located in the angular space outside the adjusting housing 55 and inside the cylindrical extension 58 on head 20. This seal prevents leakage between the head and housing 55 and also prevents relative rotation between the two which might disturb the adjustment of the fuse.

Return flow through orifice 23 advantageously serves to wash out the orifice and to remove any particles of solid matter which might alter the metering adjustment. Such particles escape into the bores 41 from the communicating counterbore 49.

In assembling the fuse the parts are successively introduced into housing l3 from the end from which coupling element l5 has been removed. A bearing washer 59 having a chamfered interior 6!] to permit free access to passages I9, and a spring washer 6| are located between the head 20 and the shoulder 62 inside coupling [5. The spring washer insures adequate pressure to hold the assembled elements in engagement with each other inside the fuse without the necessity of impractically close tolerances which would otherwise be necessary to transmit l theriiecessary pressure to:.the elements inside: the. housing.

- :In' Figz his :illustratedTthe :adaptation.-.of "the present. invention ;to aiuse of the type-:shownin Waterman: Patent. 2,354,161.. As here. shown the :valve which correspondsatothe -.-va'lve -Hl of .said patent-isheld:againstimovementby a piston"?! in which-blocks escape10f fluid; from the fuse and";ipreventswmovementof said valvexbyreason of engagement :oflthepiston extension.12 .there- With; :until' rpiston' :1 l is moved by: fluid now clear of 'the' valverseat 1'3. In E'the ilatterspositiomit uncovers: ports 14. through" which flow may reach therexit orifice '15 of? the:fuse-.'|6.

.Astrhere-"shown the cylindrical extension TI- carried. by the. :brakeicylinder 718 *fitsi inside and bears against .awreduced icylindrica-l portion 19 0f the fuse housing- 80. -Flow enteringithepassage 8| enters the angularipassagei' flz around the brake cylinder throughpassages?- in the :end ofrth'e brake: cylinder. Passage *8! leads through ports '84 to the interiorispace 85whereinthe flow operates ontvalve IO-as explained: inrsaid Waterman patent. The brake ondashpot piston 86 retards movementof valveflfl soas to affect acmeteringr actioncdescribed in said Watermanpatent.

"Asexplained: aboveconnection: with: the iormrof fuse" shown in "Fig: l, the piston': valve H readily. advances and opens" ports 14.: under fluid: :pressurezagainstsspning 8! without involvingra; substantial .pressurexrdrop;

explained? inconnection with the :form. 'of' fuse shown ::in Fig: 1 and :actsnrrtvalve. 'l 0 :to" return the same'ctotfinitial position: .Inxthisc'case "fluid enters brake cylinder 18through;check valve' 89 which on forward 1 travelz is closed: rand :obliges fluid T'llO escape only"througlrthemetering :orifioe 9Q.

' Thetmetering orifice.iscOntained in a replaceable orifice fitting 91 which' is. "held' in place :by the annular set soreW QZ.

' The several elementsfiinside:the fuse housing are introduced therein :onrassembly'. through. the end carrying: theuremovable: icouplingi element 93'. An annularclampingfscrew'il l bearsagain'st thefiendaofithe' brake cylinder and" presses it against the: cylinder 95 carryingflpiston ill. A seal 96 prevents::by=passing.5offluid aroundpistoni'H.

If desired, both types of fuse may be-.zmade insensitive ate operation? by .any i-predetermined minimumirate "of: flow; For exaniple,: if the "system "involve normal: leakage? tpast ipistons," etc such new as isareprese'nted. bythedakage may be permitted topassv theifuseswithouti'inducing operation. Also, theslfuse may bezmade .to:operate only when the :flowrexceeds. a predeterminedrate. The" fuse may be given .the? aforesaidrfimctionsxby providing a control port, inithisx-case; the "port-=97 in 'valvessrefi and. 85, whose size is: designed to permit the :aforesaidzlimitedfiow without involvingoperationtof the fuse. .Ihusz flow'rmay bypass pistons 26 "and .H without. inducing -operation until it exceeds the predetermined value in which case these pistons will be operated-fas above'described. In the event theviscosity of the fluid varies considerably it is preferable: that the orificefi'lwbegiven av sharp edge to-v minimize the effect of variation-in viscosity.

Springs 28 and 81in the respective: illustrative fuses may without. harmbe muchstronger than 6 necessary. merelyafto counteract gravity, inertia, etc; sinceonly a slight additional pressurezdrop would beinvolved. In fuseswhere thereis no return'flowtwhich .is utilized .to .return the valves to initial position) thesersprings'may be used to return the valves; andifor that purpose may advantageously be; made stronger for a quicker return. Thevolunie displaced. by the returning V3,].V6iS.S0"Sm8J1 that if there be no orifice 91 in the check'valves the necessary-small volume of return flow for this purpose will readilybe drawn intothe. housing by-leakage past the piston valve'26or1l.

Obviously the: invention is not. limited to the details of the illustrative fuses nor to. the specific type of. fuses here shown. Moreover it is not indispensable that all features of the invention be used'conjointly since-various'features. may be used to advantage-in different combinations and subcombinations.

- Having. describedimy invention, I claim:

1. In a fuse'of' the character described, the combination comprising a housing adapted to be incorporated in a fluid line, a valve seat in said housing, a normally open valve exposed to and adapted to be. moved by fluid flow toward said seat, said housing having a discharge orifice, an orificeclosure: responsive to fluid pressure in said housing for opening said orifice, said closure having a device holding said valve against closing movement and movable with said closure on opening of said orifice to permit said valve to move.

2. In a fuse of the character described, the combination comprising a housing adapted to be incorporated in a fluid line, a valve seat in said housing-,- anormally open valve in said housing exposed to and adaptedto be moved by fluid flow toward said seat; said housing having a discharge orifice, a spring pressed'piston closing said orifice and yieldableinres-ponse to fluid pressure insaid housing to open said orifice to permit iiow through said'housingand a .device. carried by said piston and engagingisaid valve to hold the latter open, said device being'movable with said piston to release said.valveuponopening of said orifice. 3. In a" fuse of the character described, the combination comprising a housing adapted to be incorporated in a fluid line, avalve seat insaid housing, a. normally openval've in. said housing exposed to. fluid :fiow-and' adapted c be moved towardsaidrseatcineresponse to flow, said housing: having a-discharge orifice: through which fluid flow passes, .anorifice closure normally closing said orifice during periods of absence-offluid flow andradapted-in-said=nernially closed position to prevent-movement of said-vaiveiinresponseto fluidsflow; said closure'being movablein response towfiu'id pressure to iopen-rs'aidroriiice and thereby toopermtt said' valve to move, and. a oheck va'lve inzsaidchousingtopermitreturn flow to 'pass said clesure.

A'I'fUSE'Of thecharacterdeseribcd, comprising in combination a housing having a fluid passage and valve. seat therein; a normally open valve: exposed tonfiuid new .andzmovablert said seat inzvresponse tofiuidnfiow'ithrough cl housing to c'losevsaidvhousing against further Iiow after a p redeterminedi' volume; of flow; 1d. .nousing having. aedischarge's'orificex'th'rough h said flow passes, a piston GlOSillgESfild'Ol'lfiCE duringperiods of nofflow andyiel'dable in response to fluid pressure to open said orificerrto': permit flow through the. housing; saidvpiston.-.ahaving1 an extension thereon engaging said valve while said piston is in closed position to prevent movement of said valve under forces of gravity and inertia.

5. A fuse of the character described comprising in combination a housing having a longitudinal passage thereto and adapted to be connected in a fluid line, a cylinder in said housing and spaced therefrom to provide fluid passages around said cylinder, a valve seat in said housing, a pieton valve slidable in said cylinder and exposed to fluid flow and movable in response to fluid flow toward said seat to cut ofl? flow through said housing, said housing having a discharge orifice therein, a closure in said housing adapted to block said orifice, a spring biasing said closure to block said orifice during periods of no flow, an extension carried by said closure and engaging said valve to hold the same open against forces of gravity and inertia, said closure being yieldable under flow pressure to open said orifice and move said extension out of engagement with said valve, and a check valve in said closure to permit return flow to pass through said housing without moving said closure.

6. A fuse of the character described comprising in combination a housing having a longitudinal passage thereto and adapted to be connected in a fluid line, a cylinder in said housing and spaced therefrom to provide fluid passages around said cylinder, a valve seat in said housing, a piston valve slidable in said cylinder and exposed to fluid flow and movable in response to fluid flow toward said seat to cut off flow through said housing, said housing having a discharge orifice there in, a closure in said housing adapted to block said orifice, a spring biasing said closure to block said orifice during periods of no flow, and an extension carried by said closure and engaging said valve to hold the same open against forces of gravity and inertia, said closure being yieldable under fluid pressure to open said orifice and move said extension out of engagement with said valve.

7. A metering device of the character described comprising in combination a housing adapted to be incorporated in a fluid line, a

cylinder in said housing and spaced therefrom to provide passages around the cylinder for fluid flow, a valve seat in said housing, means including a piston valve in said housing and movable in response to fluid flow toward said seat to cut off flow after a predetermined volume of flow, and a device longitudinally adjustable relative to said cylinder to engage the piston valve in its open position to adjust the length of stroke of said piston valve and thereby to vary the volume metered.

8. In a fuse of the character described, the combination comprising a housing adapted to be incorporated in a fluid line, a valve seat in said housing, a normally open valve in said housing exposed to and adapted to be moved by fluid flow toward said seat, said housing having a discharge orifice, a spring pressed piston closing said orifice and yieldable in response to predetermined fluid pressure to open said orifice and thereby to permit said valve to close under the pressure of fluid flow, and a device carried by said piston and engaging said valve to hold the latter open, said device being movable with said piston to release said valve upon opening of said orifice, said piston having therein a passage of predetermined size to permit a predetermined flow through said housing before development of sufiicient fluid pressure on said piston to move the same, said piston being adapted to move to open said orifice when the flow through said passage exceeds a predetermined maximum.

9. In afuse of the character described, the combination comprising a housing adapted to be incorporated in a fluid line, a valve seat in said housing, a normally open valve in said housing exposed to fluid flow and adapted to be moved toward said seat in response to fluid flow, said housing having a discharge orifice through which fluid flow passes, an orifice closure normally closing said orifice and thereby preventing closing movement of said valve, said closure being movable in response to a predetermined pressure of fluid to open said orifice and thereby to permit said valve to move, said orifice closure having therein a passage to permit limited flow through said housing, and means for resiliently holding said closure in closed position and adapted to yield under the force of fluid pressure existing when the flow through said passage exceeds a predetermined maximum.

10. In a fuse of the character described the combination with a fluid pressure line of a housing having therein a valve seat, a normally open valve adapted to be set in retracted open position and moved by the force from the flow of fluid from said retracted position toward its seat to interrupt fluid flow, a device exposed to fluid pressure and sensitive to pressure differences incident to the flow of fluid for holding said valve against movement toward its seat under extraneous forces during periods of interruption of fluid flow, said device moving under the pressure incident to resumption of fluid flow to release said valve to permit the same to move toward its seat under the force of fluid flow, said device having check means releasable on reverse flow to allow return of said valve to retracted position by said reverse flow.

11. In a metering device of the character described, the combination comprising a housing adapted to be associated with a fluid line, a valve seat in said housing, a piston valve slidable said housing toward said seat and arranged to be set in retracted open position, metering means for displacing said piston valve toward said seat at a rate corresponding to the rate of fluid flow in said line, the length of travel of said piston valve toward said seat determining the volume of flow in said line before seating of said valve, and an adjustable stop in said housing for adjusting the limit of the retracted position of said piston for varying the volume metered before seating of said valve.

12. A metering device of the character described comprising in combination a housing adapted to be incorporated in a fluid line, a valve seat in said housing, a piston and valve in said housing slidable from a normally retracted position toward said seat, metering means for displacing said piston toward said seat at a rate corresponding to the rate of fluid flow through said housing to cut off flow after a predetermined volume of flow has passed through the housing, and adjustable screw means adapted to engage said piston and valve in its retracted position to vary the length of stroke of said piston thereby to vary the volume metered before closing of said valve.

13.'In a fuse of the character described the combination with a fluid pressure line of a housing having therein a valve seat, a normally open valve adapted to be moved by the force of the flow of fluid toward its seat to interrupt fluid flow, a light weight check piston engaging said valve during periods of interruption of flow to hold said valve against movement toward closing position under forces other than those of fluid flow, a light spring for holding said check piston in its valve engaging position against forces other than fluid flow, said spring being readily yieldable under low fiuid pressure diferences against said check piston incident to resumption of fluid flow to release said valve to move toward said seat.

DONALD A. STARK.

REFERENCES CITED The following references are of record in the file of this patent:

Number UNITED STATES PATENTS Name Date Neely Aug. 14, 1894 Brown Sept. 14, 1909 Spillan May 13, 1913 Spillan Aug. 5, 1913 Brown Jan. 13, 1931 Vickers Oct. 12, 1937 Waterman July 18, 1944 Waterman Apr. 6, 1948 

